Presently, varieties of carbon nanomaterials represented by the carbon nanotube have been developed. The carbon nanomaterials are regarded as a promising material with a variety of functions in various applications such as conductive fillers, heat-conducting materials, light-emitting elements, electrode materials of a capacitor or battery, junction electrode materials of wiring materials or wirings, reinforcement materials, and black pigments.
However, the carbon nanomaterials form aggregates generally when they are produced, making it very difficult to disperse them sufficiently. Because of this, the advantageous properties of the carbon nanomaterials cannot be obtained fully when a product made of the carbon nanomaterials is manufactured.
Conventional methods to improve the dispersibility of the carbon nanomaterials are disclosed, for example, in three patent literatures, JPA-2007-169121, JPA-2008-138039, and JPA-2009-67933.
In the method disclosed in JPA-2007-169121, the carbon nanotubes are dispersed by using a non-ionic dispersing agent prepared in such a way that the amine number of the dispersing agent is set within a predetermined range. In the method disclosed in JPA-2008-138039, polyimide varnish, in which the carbon nanofibers are dispersed in the presence of a dispersing agent and an amine compound, is used. In the method disclosed in JPA-2009-67933, a carbon nanotube coating composition containing an organic dye derivative or a triazine derivative having an acidic functional group, and a dispersion resin with an amino group is used. However, the dispersibility of the carbon nanofiber is not sufficient in the presence of highly concentrated carbon nanofibers in these conventional methods. In particular, the dispersion stability has plenty of room for improvement.